A pathologic diagnosis is the result of a complex series of activities, mastered by the pathologist. The nature of these activities is, however, rarely talked about in depth. The medical literature occasionally discusses aspects of the pathologic diagnosis processes, generally departing from the pathologic practice. The lack of a model makes discussions about the subject a matter of preference or personal style. Educational programs are largely based on the apprenticeship model, and the development of specific abilities rests on the personal aspects of both apprentice and mentor. A model for the pathologic diagnostic process is proposed. The process of diagnosis can be viewed as an action plan, encompassing 4 domains: (1) cognitive, (2) communicative, (3) normative, and (4) medical conduct. The cognitive domain involves processes of perception, attention, memory, search, hypothesis creation, and verification, among others. Communicative skills consist of providing arguments in support of a diagnostic conclusion, with adequate clinical and relevant pathologic information. Pathologic diagnosis is also subject to technical rules (based on empirical experiences), rules of rational choice (strategies aiming at definite goals), and consensual rules among peers. Finally, the pathologic diagnosis has to be evaluated in the sphere of medical conduct, from the perspectives of both the pathologist and the referring clinician. An understanding of the diagnostic process from a theoretic perspective will benefit pathology as a science and a medical specialty because it provides the basis for understanding diagnostic variations and discrepancies. Pathologic difficulties or errors can be mapped, allowing the institution of specific remedies. This model may also enhance training and educational strategies because specific emphasis can be directed toward a particular difficulty.